1. Field of the Invention
The present invention relates to a sheet stacking device that stacks discharged sheets on a discharge tray, and a printing apparatus.
2. Description of the Related Art
When images have been printed on sheets (printing media), such as paper sheets, by a printing apparatus, generally, the sheets are discharged to and stacked on a discharge tray that is included in a post-processing device. In Japanese Patent Laid-Open No. 2006-273561, the arrangement wherein presser members used to hold down the sheets that are discharged on a discharge tray is described in order to obtain registration of the sheets discharged on the discharge tray. The presser members pivot downward to move to a pressing position to hold down the sheets on the discharge tray, or pivot upward to move to a retraction position apart from the discharge tray, and is to be turned up or down in synchronization with the discharging operation for discharging the sheet to the discharge tray. That is, when the presser members are located at the pressing position to hold down the sheets stacked on the discharge tray, the presser members are moved to the retraction position before the next sheet (the succeeding sheet) is discharged to the discharge tray, and are moved to the pressing position after the succeeding sheet is discharged to the discharge tray.
According to the printing apparatus described in Japanese Patent Laid-Open No. 2006-273561, since the presser members are moved to the retraction position before the succeeding sheet is discharged, and are moved to the pressing position after the succeeding sheet has been discharged, there is a possibility that the positions of the stacked sheets might be deviated when the succeeding sheet is discharged. In other words, when the succeeding sheet is discharged, the stacked sheets are not held down by the presser members, and therefore, the portion of the succeeding sheet, particularly, the leading edge of the succeeding sheet, might slide across the surface of the topmost sheet on the stack, and cause deviation of the stacked sheet. Furthermore, when the presser members pivot upward to move from the pressing position to the retraction position, the stacked sheet may be caught and flipped up. As a result, there is a possibility that the positions of the sheets discharged on the discharge tray might be deviated.